Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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FXUS62 KRAH 031318

Area Forecast Discussion
National Weather Service Raleigh NC
920 AM EDT Mon Oct 3 2022

The remnants of Ian will remain stalled out over the Mid Atlantic
coast through early Wednesday, keeping our weather cool and
unsettled. The low will finally push east and offshore Wednesday,
bringing warmer weather for Thursday and Friday. A cold front will
approach from the northwest late Friday, and move through the area
early Saturday.


As of 920 AM Monday...

Only minor forecast tweaks needed this morning. Morning stratocu
have broken up over the far W CWA, but thicker/lower stratus
persists over the E half, as vorticity lobes and deeper moisture
both pivot around low pressure evident from the surface up through
the mid-upper levels over and just off the VA coast. The chance for
low-qpf but high-coverage light rain or drizzle will linger through
much of today across the NE with a steady feed of low-level Atlantic
moisture, a persistent deep (8-10 kft) near-saturated layer, and
high low-level stability to inhibit dispersion in the vertical.
We`re still on track to reach highs in the mid-upper 50s to the N
and E of the Triangle to the low-mid 60s to the S and W. -GIH

Earlier discussion from 330 AM: Water vapor satellite showed a ridge
stretching north from TX into the Midwest, and Ian`s remnant upper
low over VA/MD. Surface obs showed Ian`s remnant low sitting off the
VA coast, and a 1030 mb high over MI. Moist, north northeasterly
flow was helping to generate patchy, light showers/drizzle across
the region overnight as weak vorticity lobes looped around the upper
low and across our area. Cloudy skies will start to clear across
western areas today as the surface low moves slightly northeast,
however moist, upslope flow will maintain low clouds elsewhere. A
tight pressure gradient between the low and high to our north will
create breezy winds through the period, with areas across the NE
Piedmont and Coastal Plain gusting to around 30 mph. Highs today
will be chilly where skies remain cloudy. Afternoon temps will range
from the mid-50s NE to mid-60s SW, which is 10 to 20 degrees below
seasonal normals.

A shortwave will merge with the upper low to our north and swing
across the region later tonight, helping to generate a round of
light showers, mainly east of US-1. Breezy winds from today will
mostly diminish tonight, however some brief gusts to 20 mph may
surface in showers. Lows tonight will be in the mid-40s.


As of 400 AM Monday...

The surface low off the VA coast will move slightly further
northeast Tuesday, however the upper low to our north will begin to
dig southeast across eastern NC. Cold air advection and northerly
flow will continue cloudy conditions across eastern areas for
another day, with highs only expected to be a degree or two higher
than Monday. A few weak vort lobes will help create the possibility
of a shower or two across the NE Piedmont and Coastal Plain on
Tuesday as the upper low moves closer to central NC. Precipitation
chances will decrease overnight as conditions become more stable,
with lows again in the mid-40s.


As of 320 AM Monday...

Wed: The pesky mid-level trough that has been over the area tied to
the remnants of Ian is forecast to be off of VA/NC early Wed. The
system will finally move east-northeast towards the north Atlantic
by early Thu, aided partially by a shortwave over the upper
Mississippi Valley pushing east into the Ohio Valley come early Thu.
At the surface, while differences remain amongst the guidance, a
coastal low will be located roughly off the coast of VA and south of
the Delmarva region. A gusty northwest flow will persist at the
surface as a result. A moist low-level low will continue, especially
across the eastern Piedmont and Coastal Plain, as forecast soundings
from the NAM/GFS continue to indicate saturation in the 925 to 800
mb layer. This should favor morning stratus and afternoon
stratocumulus, especially in the east, limiting highs there 10
degrees below normal in the middle 60s. More insolation is expected
to the west, with highs reaching the upper 60s to lower 70s, about 3-
5 degrees below normal. No real chance of rain/drizzle as the
exiting of the trough will favor height rises and stable conditions
aloft. Weak high pressure settles in Wed night as ridging aloft
builds in. Good radiational cooling will be favored across the west,
where low clouds will scatter out faster, generally low to middle
40s. To the east, lows will be close to the mid to upper 40s.

Thu-Sun: Not a lot of change in the overall pattern during this time
frame compared to the previous forecast package. A warming trend
will ensue Thu-Fri as riding will transition to a more zonal west-
southwest flow at mid-levels. High pressure will be situated off the
SE US with low-level thicknesses rising to 1385 to 1395 m, favoring
near normal highs Thu in the mid to upper 70s and above normal
temperatures (4-8 degrees) Fri in the upper 70s and lower 80s. Fri
will be the pick day of the week.

A cold front is still poised to move through sometime late Fri night
and early Sat, with most ensemble guidance showing a chilly 1028 mb
high settling into the Appalachians early Sun. Model guidance
continues to differ on the trough that will ultimately push the
front through the area. The GFS/Canadian show a more closed
shortwave trough over the Great Lakes Fri, moving into the NE US
late Sat, while the ECMWF is generally flatter and more zonal over
our area. Regardless, the passage continues to be dry, though maybe
a few sprinkles early Sat are possible. The differences manifest as
slightly higher low-level thicknesses on Sat/Sun in the ECMWF versus
the GFS/Canadian. Ensemble clusters appear to favor the GFS/Canadian
and would favor highs below normal in the low/upper 60s Sat and
low/mid 60s Sun.

As for low temperatures Sun morning, given model spread mentioned
above, uncertainty still exists, but it is possible we could see
patchy frost in outlying areas with low-level thickness at/below
1340 m behind the front. As context, the NBM 75th percentile shows
middle 30s in outlying areas of the Piedmont and upper 30s/low 40s
elsewhere. The earliest first date with minimum temperatures
at/below 36 degrees in central NC is generally between Oct 7 and 14,
compared to the median first date of late October to early November.
This will be something to keep an eye on for sure as we get closer.
For now, followed the NBM 50th percentile in the low/mid 40s with
upper 30s in the cooler spots.


As of 630 AM Monday...

Widespread IFR-MVFR ceilings will continue this morning, along with
periods of light rain or drizzle. Ceilings will lift across the
Triad later this morning, but linger across the NE Piedmont, Coastal
Plain and Sandhills throughout the day. Breezy northerly winds are
expected today due to nearby low pressure, with areas across the
east gusting to near 25 kt. An isolated shower is possible near KRWI
throughout the day, and near KFAY/KRWI/KRDU tonight as a weak
disturbance moves across the area.

Outlook: Sub-VFR conditions from low clouds will continue Tuesday,
along with an isolated shower or two near KRWI. Sub-VFR ceilings are
possible at times through mid week, then VFR conditions are expected
for the end of the week across the region.




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